The invention relates to a method for the adhesive application of a lubricant layer to an exposed, frictionally stressed surface of an object, and to an object with a lubricant layer adhering to an exposed surface, as are both known, for example, from the article which forms the basis of the precharacterizing clause xe2x80x9cFormation and self-lubricating mechanisms of boric acid on borided steel surfacesxe2x80x9d by A. Erdemir et al. in Surface and Coating Technology 76-77, 1995, pp. 443-490.
The invention relates to a method for the adhesive application of a lubricant layer to an exposed, frictionally stressed surface of an object, and to an object with a lubricant layer adhering to an exposed surface, according to the preambles of claims 1 and 30, respectively, as are both known, for example, from the article which forms the basis of the precharacterizing clause xe2x80x9cFormation and self-lubricating mechanisms of boric acid on borided steel surfacesxe2x80x9d by A. Erdemir et al. in Surface and Coating Technology 76-77, 1995, pp. 443-490.
The article xe2x80x9cFormation and self-lubricating mechanisms of boric acid on borided steel surfacesxe2x80x9d by A. Erdemir et al. in Surface and Coating Technology 76-77, 1995, pp. 443-490 has disclosed a coating of a dry lubricant made from boric acid on steels and a method for applying the coating. In the method which is known from this document, a steel is firstly borided. The borided surface of the steel has a good hardness and resistance to corrosion. However, its coefficient of friction is very high. Therefore, the borided surface of the steel is provided with a lubricant layer of boric acid, which acts as a dry lubricant. For the boriding, the steel is immersed in a salt bath which contains a boron compound and is heated to 940xc2x0 C. After the salt bath, the borided steel is heated to 750xc2x0 C., allowing the boron atoms to diffuse more deeply into the surface region of the steel. It is assumed that some of the atoms also diffuse at the free surface, where they immediately react, in the presence of oxygen, to boron oxide. As a result, a boron oxide layer, which during the subsequent cooling and in the presence of hydrogen is converted into boric acid, is deposited on the surface of the steel. However, to form the boron oxide the temperature must not be reduced to less than 750xc2x0 C., and the borided steel must also be heated to this temperature for no longer than 8 min, since otherwise no boron oxide is formed. Apart from the fact that this heat treatment represents an immense load on the steel, the process for producing the boron oxide layer is highly sensitive, and consequently the known method is very involved, complicated and expensive. Furthermore, it is difficult to produce near net shape, in particular accurately dimensioned components using this method, and a high reject rate is involved. Also, the entire method is highly inflexible, in particular for changing layer thicknesses.
The article xe2x80x9cA study of the formation and self-lubrication mechanisms of boric acid films on boric oxide coatingsxe2x80x9d by A. Erdemir et al. in Surface and Coating Technology 43/44, 1990, pp. 588-596 has likewise disclosed a coating of a dry lubricant comprising boric acid and a method for applying this coating. In this method, the surfaces of an object made from alpha-alumina and an object made from steel (M50) were cleaned by an argon ion beam and were then coated with the boron oxide in vacuo by means of electron beam evaporation. In both cases, the coefficients of friction of the lubricant layers, which were a few xcexcm thick, were very good, although the service life of the coating on steel was short. Furthermore, the adhesion of the lubricant layers made from boric acid to the substrates was low, and consequently this method also involves a high reject rate.
The object of the invention is to provide a method with which in particular a metallic object can be provided with a successfully adhering lubricant layer of a dry lubricant at low cost, within tight manufacturing tolerances and with low reject rates, the intention being that the dry lubricant should have the lowest possible coefficient of friction and the longest possible service life. A further object of the invention is to develop a successfully adhering lubricant layer of a dry lubricant for in particular a metallic object, which lubricant layer is applied at low cost, within tight manufacturing tolerances and with low reject rates, the dry lubricant having the lowest possible coefficient of friction and the longest possible service life. The layer structure according to the invention and the application of the individual layers, preferably by means of a plasma Chemical Vapor Deposition (CVD) process, allow the layer thicknesses to be applied reproducibly in the xcexcm range in a simple manner, so that at least one complex remachining step can be dispensed with. Furthermore, the adhesion to the object is improved by the procedure according to the invention.